I'm always suspicious of people taking what's already a pretty small group of stuff and then dividing it down even further. I'm also very, very, very suspicious of people using Roman Numerals, they frequently show up and make an appearance when the author wants to impart a a patina of scientific or intellectual legitimacy to their silly groupings. Perhaps we just love taxonomy as a species (and we do), but it tends to be more for amusement or aspiring to superiority than anything real. Octoroon, quadroon and other such terms arose in slavery (and note the 'Latin' base for the word, that pseudo-intellectual deal again), but despite such fine hairsplitting did nothing, as all were considered slaves. So 'type IV' or 'type V' (How many sub-types are there? Do you ever get to change sub-types, or like Octoroon is a permanent condition? Can anyone be more than one at the same time?)
If I ever think of something we have in common I will be surprised.